Re: [RFC] Make the SCSI mempool allocations variable

[Jeremy Higdon <jeremy@sgi.com>]

On Tue, Mar 09, 2004 at 02:02:55PM -0500, James Bottomley wrote:
> Based on Jeremy's request to increase max_phys_segments, this is the way
> to do it (SCSI_MAX_PHYS_SEGMENTS) is the value that gets set as the
> queue's max_phys_segments.
> 
> I have to say that when I tried raising it to 256 and hammering a 10GB
> ext2 filesystem, I still didn't generate any >128 segment requests, so
> I'm dubious that raising it has any benefit at all, but feel free to try
> it and publish the figures.
> 
> I did wonder if lowering it might help improve the memory footprint for
> some embedded systems, so I set it up to be lowered as far as 32.
> 
> James

Thanks, James!

I promise that we will take advantage of this, but it might take a
couple of months.  As you point out, the filesystem code also has
to deliver the larger requests.

I'll try a couple of tests with XFS and block device direct I/O.

jeremy